API Violation - Multiple Calls Made to -[Xctestexpectation Fulfill]

XCTestExpectation: how to avoid calling the fulfill method after the wait context has ended?

Yes, there is a much simpler way to avoid this API violation issue: just declare your expectation variable as __weak. Although not clearly documented, the expectation will be released when the timeout expires. So if the task takes longer than the timeout, the expectation variable will be nil when the task completion handler is called. Thus the fulfill method will be called on nil, doing nothing.

- (void) test1TaskLongerThanTimeout
{
    __weak XCTestExpectation *expectation = [self expectationWithDescription:@"Test 1: task longer than timeout"];
    [self startAsynchronousTaskWithDuration:4 completionHandler:^(id result, NSError *error) {
        XCTAssertNotNil(result);
        XCTAssertNil(error);
        [expectation fulfill];
    }];
    [self waitForExpectationsWithTimeout:2 handler:nil];
}

Asynchronous Performance Tests with XCTest

With some help from Apple, I have a solution. Silly oversight on my part as this is very easy to solve. To get to work, all you need to do is put the creating of the expectation object (clsQueryReturnedExpectation) inside the measureMetrics block so it is created afresh each time the performance test is run.

PFCLSClient *theClient = [[PFCLSClient alloc] init];

[self measureMetrics:@[XCTPerformanceMetric_WallClockTime] automaticallyStartMeasuring:YES forBlock: ^{
    XCTestExpectation *clsQueryReturnedExpectation = [self expectationWithDescription:@"clsQuery returned"];  
    [theClient getStructureOfType:clsImageTypeSVG ForID:idString success: ^(NSDictionary *structureInfo) {
       [clsQueryReturnedExpectation fulfill];
    } failure: ^(NSError *error) {
       XCTFail();
       [clsQueryReturnedExpectation fulfill];
    }];

   [self waitForExpectationsWithTimeout:5 handler: ^(NSError *error) {
        [self stopMeasuring];
   }];
}];

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